diff --git a/build-constraints.yaml b/build-constraints.yaml
index 50453e4c..d3e2cd49 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -5143,6 +5143,7 @@ packages:
       # https://github.com/commercialhaskell/stackage/issues/5747
       - http-client < 0.7
       - http-client-openssl < 0.3.3
+      - req < 3.9.1
 
       # https://github.com/commercialhaskell/stackage/issues/5836
       - clock < 0.8.2